Contents

• Public Types
• Public Functions
• Public Variables
• Related Non-Members
• Detailed Description

Detailed Description

TheQStyleOption class stores the parameters used byQStyle functions.

QStyleOption and its subclasses contain all the information thatQStyle functions need to draw a graphical element.

For performance reasons, there are few member functions and the access to the member variables is direct (i.e., using the. or-> operator). This low-level feel makes the structures straightforward to use and emphasizes that these are simply parameters used by the style functions.

The caller of aQStyle function usually createsQStyleOption objects on the stack. This combined with Qt's extensive use ofimplicit sharing for types such asQString,QPalette, andQColor ensures that no memory allocation needlessly takes place.

The following code snippet shows how to use a specificQStyleOption subclass to paint a push button:

void MyPushButton::paintEvent(QPaintEvent*){QStyleOptionButton option;    option.initFrom(this);    option.state= isDown()?QStyle::State_Sunken :QStyle::State_Raised;if (isDefault())        option.features|=QStyleOptionButton::DefaultButton;    option.text= text();    option.icon= icon();QPainter painter(this);    style()->drawControl(QStyle::CE_PushButton,&option,&painter,this);}

In our example, the control is aQStyle::CE_PushButton, and according to theQStyle::drawControl() documentation the corresponding class isQStyleOptionButton.

When reimplementingQStyle functions that take aQStyleOption parameter, you often need to cast theQStyleOption to a subclass. For safety, you can useqstyleoption_cast() to ensure that the pointer type is correct. For example:

void MyStyle::drawPrimitive(PrimitiveElement element,constQStyleOption*option,QPainter*painter,constQWidget*widget){if (element== PE_FrameFocusRect) {constQStyleOptionFocusRect*focusRectOption=                qstyleoption_cast<constQStyleOptionFocusRect*>(option);if (focusRectOption) {// ...        }    }// ...}

Theqstyleoption_cast() function will return 0 if the object to whichoption points is not of the correct type.

For an example demonstrating how style options can be used, see theStyles example.

Member Type Documentation

enum QStyleOption::OptionType

This enum is used internally byQStyleOption, its subclasses, andqstyleoption_cast() to determine the type of style option. In general you do not need to worry about this unless you want to create your ownQStyleOption subclass and your own styles.

The following values are used for custom controls:

Some style options are defined for variousQt3Support controls:

See alsotype.

enum QStyleOption::StyleOptionType

This enum is used to hold information about the type of the style option, and is defined for eachQStyleOption subclass.

The type is used internally byQStyleOption, its subclasses, andqstyleoption_cast() to determine the type of style option. In general you do not need to worry about this unless you want to create your ownQStyleOption subclass and your own styles.

See alsoStyleOptionVersion.

enum QStyleOption::StyleOptionVersion

This enum is used to hold information about the version of the style option, and is defined for eachQStyleOption subclass.

The version is used byQStyleOption subclasses to implement extensions without breaking compatibility. If you useqstyleoption_cast(), you normally do not need to check it.

See alsoStyleOptionType.

Member Function Documentation

QStyleOption::QStyleOption(int version = QStyleOption::Version,int type = SO_Default)

Constructs aQStyleOption with the specifiedversion andtype.

The version has no special meaning forQStyleOption; it can be used by subclasses to distinguish between different version of the same option type.

Thestate member variable is initialized toQStyle::State_None.

See alsoversion andtype.

QStyleOption::QStyleOption(constQStyleOption & other)

Constructs a copy ofother.

QStyleOption::~QStyleOption()

Destroys this style option object.

void QStyleOption::initFrom(constQWidget * widget)

Initializes thestate,direction,rect,palette, andfontMetrics member variables based on the specifiedwidget.

This is a convenience function; the member variables can also be initialized manually.

This function was introduced in Qt 4.1.

See alsoQWidget::layoutDirection(),QWidget::rect(),QWidget::palette(), andQWidget::fontMetrics().

QStyleOption & QStyleOption::operator=(constQStyleOption & other)

Assignother to thisQStyleOption.

Member Variable Documentation

Qt::LayoutDirection QStyleOption::direction

This variable holds the text layout direction that should be used when drawing text in the control.

By default, the layout direction isQt::LeftToRight.

See alsoinitFrom().

QFontMetrics QStyleOption::fontMetrics

This variable holds the font metrics that should be used when drawing text in the control.

By default, the application's default font is used.

See alsoinitFrom().

QPalette QStyleOption::palette

This variable holds the palette that should be used when painting the control.

By default, the application's default palette is used.

See alsoinitFrom().

QRect QStyleOption::rect

This variable holds the area that should be used for various calculations and painting.

This can have different meanings for different types of elements. For example, for aQStyle::CE_PushButton element it would be the rectangle for the entire button, while for aQStyle::CE_PushButtonLabel element it would be just the area for the push button label.

The default value is a null rectangle, i.e. a rectangle with both the width and the height set to 0.

See alsoinitFrom().

QStyle::State QStyleOption::state

This variable holds the style flags that are used when drawing the control.

The default value isQStyle::State_None.

See alsoinitFrom(),QStyle::drawPrimitive(),QStyle::drawControl(),QStyle::drawComplexControl(), andQStyle::State.

int QStyleOption::type

This variable holds the option type of the style option.

The default value isSO_Default.

See alsoOptionType.

int QStyleOption::version

This variable holds the version of the style option.

This value can be used by subclasses to implement extensions without breaking compatibility. If you use theqstyleoption_cast() function, you normally do not need to check it.

The default value is 1.

Related Non-Members

Tqstyleoption_cast(constQStyleOption * option)

Returns a T or 0 depending on thetype andversion of the givenoption.

Example:

void MyStyle::drawPrimitive(PrimitiveElement element,constQStyleOption*option,QPainter*painter,constQWidget*widget){if (element== PE_FrameFocusRect) {constQStyleOptionFocusRect*focusRectOption=                qstyleoption_cast<constQStyleOptionFocusRect*>(option);if (focusRectOption) {// ...        }    }// ...}

See alsoQStyleOption::type andQStyleOption::version.

Tqstyleoption_cast(QStyleOption * option)

This is an overloaded function.

Returns a T or 0 depending on the type of the givenoption.